Kraft, J. R., & Baum, W. M. (2001).
Group choice: The ideal free distribution of human social behavior.
Journal of the Experimental Analysis of Behavior,
76, 21-42.
Group choice refers to the distribution of group members between
two choice alternatives over time. The ideal free distribution
(IFD), an optimal foraging model from behavioral ecology,
predicts that the ratio of foragers at two resource sites should
equal the ratio of obtained resources, a prediction that is
formally analogous to the matching law of individual choice,
except that group choice is a social phenomenon. Two experiments
investigated the usefulness of IFD analyses of human group choice
and individual-based explanations that might account for the
group-level events. Instead of nonhuman animals foraging at two
sites for resources, a group of humans chose blue and red cards
to receive points that could earn cash prizes. The groups chose
blue and red cards in ratios in positive relation to the ratios
of points associated with the cards. When group choice ratios and
point ratios were plotted on logarithmic coordinates and fitted
with regression lines, the slopes (i.e., sensitivity measures)
approached 1.0 but tended to fall short of it (i.e.,
undermatching), with little bias and little unaccounted for
variance. These experiments demonstrate that an IFD analysis of
group choice is possible and useful, and suggest that group
choice may be explained by the individual members' tendency to
optimize reinforcement.
Key words: group choice, ideal free distribution, social
behavior, matching law, card choices, humans